Contaminant amounts and effectiveness of sewage treatment from region of Września within the compass of years

Summary.

The aim of the research was to determine the parameter of contamination in sewage and the effectiveness of its treatment by the mechanical-biological sewage treatment plant located in Września in the Wielkopolska voivodeship. The research was based on data from 11 years (2001-2011) of the sewage treatment plant work. The following indicators of contamination were analysed: Biochemical Oxygen Demand for 5 days (BOD), suspended solids, total nitrogen, ammonium nitrogen, nitrate nitrogen and total phosphorus. On the basis of the received data it was observed that levels of most contaminants in sewage increased over the 11 years. It was particularly visible in the cases of suspended solids, 5-day BOD, ammonium and total phosphorus. Regardless of such tendencies, the effectiveness of sewage treatment over the studied period was satisfactory. Coefficients of contaminants reduction averaged for 2001-2011 amounted to 94% for suspended solids, 99% for 5-day BOD, 84% for total nitrogen, 99% for ammonium nitrogen and 86% for total phosphorus. It was also shown that the amount of total nitrogen in treated sewage was determined by the amount of nitrates in it, whereas concentration of total nitrogen in untreated sewage was dependent on the concentration of ammonium nitrogen.